Composite materials are of great current interest because they provide a very favorable combination of high strength and low density. Typically, a composite material is comprised of fibers of graphite, boron, glass, and the like embedded within an epoxy, phenolic or other polymer resin matrix. The more advanced composites which have particularly favorable high strength to density ratio properties are especially attractive for aerospace applications. But typical of other advanced aerospace materials they present comparative processing difficulties; they cannot be made by a simple layup of the fibers and resin followed by room temperature curing. Aerospace composite materials not only involve more difficult-to-fabricate resins but often essentially defect-free finished parts must be produced. As a result, aerospace composites are typically molded and cured at elevated temperatures under substantial pressure.
Although a variety of molding processes have been used to mold composites at elevated temperatures and pressures (e.g. compression molding, isostatic pressure molding using pressure bags or pressure vessels, pressure pad molding) there are problems (e.g. bag leaks) associated with these processes.
Accordingly, there is a constant search for composite molding processes.